Various interactive renderless online map services, such as Teraserver.Com, Google.Maps.com and ViaVirtualEarth.com, provide web based global maps to client computing devices. These services offer an enormous amount of data that includes maps of global extent with detail as fine as 25 cm/pixel aerial photography. Just as importantly, users of the client computing devices can navigate (zoom and pan) throughout that data fluidly. The enormous data sets are organized so that a web browser running on the client device can easily fetch just the part of the map data the user wants to view.
Prior-generation web map services, such as MapQuest® map services, rendered at a server a new image for each change of view requested by the client computing device. This rendering step often introduced a delay of many seconds between a request for view change and the presentation of the new view. “Renderless” services simply serve pre-rendered data, eliminating this delay and providing a fast and fluid user experience.
These services provide tiling, e.g. a collection of prior generated tile shaped small images (referred to herein as “tiles”). Thus when the user changes its view of a map, these tiles can be quickly sent over the internet to the client device. Further, as the view is panned, some of these same tiles can be re-used by being displayed at different locations on a screen of the client device. If the user decides to zoom into or out of the image, tiles would be provided from the server with pre-computed tiled images that cover more detail of the image being zoomed or that provide less detail but shows more geographical area.
Interactive renderless online map services typically offer two layers of imagery: 1) road maps and/or 2) satellite or aerial photography. The client browser can switch among alternate views of any particular geographic location, because the road maps and the aerial photographs are registered to the same coordinate system. The road data is generated by rendering geographic vector information into tiles; the aerial photography is similarly rendered by transforming geo-referenced imagery from its original projection into the Mercator projection used for the online service.
A substantial effort was involved in generating image tiles for teraserver.microsoft.com, Google.Maps.com, and VirtualEarth.com. The source maps—including road data, satellite imagery, aerial photography, and annotations—had to be registered into a common projected coordinate system, despite the fact that they came from multiple sources in various projections. The companies that produced these tiles hired geographic-information-systems experts to perform this common registration. The source maps included geo-referencing information in a well-defined projection that could be mathematically transformed into the common projection coordinate system.
There are many external source maps that predate or are otherwise unrelated to renderless online services. Maps provide different content, such as hiking trails, building floor plans, or bus routes. Source maps may cover historical data, or provide fresher data or more detail than those maps available from online services. An aerial photographer may produce current higher-resolution imagery in areas for which existing online services offer outdated, no or low-quality data.
Many of these maps contain no geo-referencing information, especially if they were generated non-electronically, such as those maps created before the development of modern geographic-information-systems techniques. The maps might not even indicate the projection in which they were drawn. Absent the claimed embodiment, the task of geo-referencing these external source maps requires expertise in geographic information systems, and even with such expertise it is a difficult, tedious, and expensive task.